A61 K 31/70, C 07 H 17/08
The invention relates to novel compounds from the class of macrolide antibiotics. Particularly, the invention relates to novel 3,6-hemiketals from the class of 9a-azalides, to their pharmaceutically acceptable addition salts with inorganic or organic acids, to a process for their preparation and to the use thereof as antibiotics or as intermediates for the synthesis of other macrolide antibiotics.
Macrolide antibiotic erythromycin A has been for more than 40 years considered as a safe and efficient agent for the treatment of respiratory and genital infections caused by Gram-positive and by some Gram-negative bacteria, some species of Legionella, Mycoplasma, Chlamidia and Helicobacter. Noticed changes in bioavailability after oral administration, gastric intolerance in many patients and loss of activity in an acidic medium whereat the inactive metabolite anbydroerythromycin is formed are basic disadvantages in the clinical use of eiythromycin. However, the spirocyclization of the aglycone ring is successfully inhibited by a chemical transformation of C-9 ketone or hydroxyl groups in C-6 and/or C-12 positions. Thus, e.g by oximation of C-9 ketone and subsequent Beckmann rearrangement and reduction, 9-deoxo-9a-aza-9a-homoerythromycin A, the first 15-membered macrolide antibiotic with 9a-amino group incorporated in the aglycone ring, is obtained (Kobrehel G. et al., U.S. Pat. No. 4,328,334; May 1982). By reductive methylation of 9-amines according to Eschweiler-Clark process, 9-deoxo-9a-methyl-9a-aza-9a-homoerythromycin (AZITHROMYCIN), a prototype of a novel class of macrolide antibiotics, namely azalides, is synthesized (Kobrehel G. et al., BE 892357; July 1982). In addition to a broad antimicrobial spectrum including also Gram-negative bacteria, azithromycin is also characterized by a long biological half-life, a specific transport mechanism to the place of use and a short therapy period. Azithromycin easily penetrates and it accumulates inside human phagocyte cells resulting in an improved action upon intracellular pathogenic micro-organisms from the classes of Legionella, Chlamidia and Helicobacter.
Further, it is known that C-6/C-12 spirocyclization of erythromycin A is successfully inhibited by O-methylation of C-6 hydroxyl group of the aglycone ring (Watanabe Y. et al., U.S. Pat. No. 4,331,803; May 1982). By the reaction of erythromycin with benzyloxycarbonyl chloride and subsequent methylation of the obtained 2xe2x80x2-O,3xe2x80x2-N-bis(benzyloxycarbonyl) derivative, by elimination of the protecting groups and by 3xe2x80x2-N-methylation, there are formed, in addition to 6-O-methylerythromycin (CLARITHROMYCIN), also significant amounts of 11-O-methylerythromycin and of multiple-substituted analogs (Morimoto S., et al., J. Antibiotics, 1984, 37, 187). With respect to erytlromycin A, clarithromycin is considerably more stable in an acidic medium and exhibits better in vitro action with respect to Gram-positive bacteria strains (Kirst H. A. et al., Antimicrobial Agents and Chemoter., 1989, 1419). In a similar manner also a series of O-methyl-derivatives of azithromycin (Kobrehel G. et al., U.S. Pat. No. 5,250,518; October 1993) was synthesized. Although the main products of O-methylation of azithromycin, namely 11-O-methyl-azithromycin (Example 8) and 6-O-methyl-azithromycin (Example 6) exhibit significant activity against standard bacteria strains and clinical isolates and pharmacokinetic properties similar to those of azithromycin, the obtaining of products in larger quantities represents an additional technical problem due to nonselectivity of O-methylation. The determination of the structure of O-methyl-derivatives of azithromycin was based on analysis of 1H-1H and 1H-13C 2D NMR spectra (300 MHz). Subsequently, it was additionally determined by long-range NMR spectroscopy that substitution on C-6 hydroxyl group had been erroneously ascribed to azithromycin and that actually 12-O-methyl-azithromycin was in question. Further it has been found that the use of suitable protecting groups on hydroxyl groups in 4xe2x80x3- and 11-positions (especially of silyl protecting groups such as trimethylsilyl groups) results in selective O-methylation and makes possible a simple preparation of 12-O-methyl-azithromycin (HR 970051A; October 1997). Later, Waddell S. T. et al., (Biorg. Med. Chem. Letters 8 (1998), 549-555), independently of the latter patent application, established O-methylation of hydroxyl group in C-12 position.
It is known as well that recent research on 14-membered macrolides has lead to the discovery of a new type of macrolide antibiotics, namely ketolides. Instead of the neutral sugar L-cladinose known for its unstability even in a weakly acidic medium, these compounds possess a keto group on C-3 position (Agouridas C. et al., EP 596802 A1, May 1994; Le Martret O., FR 2697524 A1, May 1994). Ketolides show a significantly better action against MLS (macrolide, lincosamide and streptogramin B) induced-resistant organisms (Jamjian C., Antimicrob. Agents Chemother., 1997, 41, 485). This important discovery has led to a large number of 3-keto derivatives of clarithromycin, mostly substituted on C-11/C-12 positions, yielding numerous cyclic carbonates, carbamates and, recently, carbazates. The first step of the synthesis of ketolides includes the hydrolysis of clarithromycin under the formation of a corresponding 3-decladinosyl derivative, (3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-derivative), which is, after the removal of the protection of 2xe2x80x2-hydroxyl group (preferably by acylation with chlorides or anhydrides of carboxylic acids), subjected to a reaction of oxidation and deprotection of 2xe2x80x2- position. According to our knowledge C-11/C-12 substituted ketolides from the class of 9a-azalide antibiotics have hitherto not been described. The first step, namely the synthesis of 3-decladinosyl-derivatives of 9-deoxo-9a-aza-9a-homoerydiromycin and azithromycin, is described in U.S. Pat. No. 4,886,792, December 1989. With intention to oxidize C-3 hydroxyl group of 3-decladinosyl-azithromycin and its 11-O-methyl- and 12-O-methyl-derivatives by transannular addition of 6-hydroxyl group onto the newly formed C-3 ketone there has been obtained a hitherto not described series of bicyclic and tricyclic 3,6-hemiketals from the class of 9a-azalides.
The synthesis of 3,6-hemiketals of azithromycin and O-methyl derivatives thereof comprises the preparation of corresponding 3-decladinosyl derivatives, the protection of 2xe2x80x2-hydroxyl group of the basic sugar, D-desosamine, by selective acylation, the oxidation of the hydroxyl group in C-3 position, the deprotection of 2xe2x80x2-position and the cyclization of C-11 and C-12 hydroxyl groups. Objects of the present invention are also pharmaceutically acceptable addition salts of 3,6-hemiketals of azithromycin and its O-methyl derivatives with organic and inorganic acids, methods and intermediates for their preparation, as well as preparation and application methods of pharmaceutical preparations.
The invention relates to
i) novel 3,6-hemiketals from the class of 9a-azalides,
ii) a process for the preparation of novel 3,6-hemiketals from the class of 9a-azalides.
iii) use of novel 3,6-hemiketals from the class of 9a-azalides as antibiotics or as intermediates for the synthesis of other macrolide antibiotics.
Novel 3,6-hemiketals from the class of 9a-azalides of the general formula (I) 
characterized in that
R1 individually stands for hydroxyl, L-cladinosyl group of the formula (II) 
wherein
R2 individually stands for hydrogen or a silyl group,
R3 individually stands for hydrogen or together with R6 stands for an ether group,
R4 individually stands for hydrogen, (C1-C4)acyl group or xe2x80x94COOxe2x80x94(CH2)nxe2x80x94Ar group, wherein n is 1-7 and Ar individually stands for an unsubstituted or substituted aryl group with up to 18 carbon atoms,
R5 individually stands for hydrogen, methyl group or xe2x80x94COOxe2x80x94(CH2)nxe2x80x94Ar group, wherein n is 1-7 and Ar individually stands for an unsubstituted or substituted aryl group with up to 18 carbon atoms,
R6 individually stands for a hydroxyl group or together with R3 has the meaning of an ether group,
R7 individually stands for hydrogen, (C1-C12)alkyl group, silyl group or together with R8 and C-11/C-12 carbon atoms stands for a cyclic carbonate,
R8 individually stands for hydrogen, (C1-C12)alkyl group, silyl group or together with R7 and C-11/C-12 carbon atoms stands for a cyclic carbonate,
and their pharmaceutically acceptable addition salts with inorganic or organic acids, are obtained by the following steps.
Step 1
Azithromycin of the general formula (I) wherein R1 stands for L-cladinosyl group of the formula (II), R2, R3, R4, R7 and R8 are mutually the same and stand for hydrogen, R5 is methyl and R6 is a hydroxyl group, is subjected to a reaction with organic carboxylic acid chlorides of the formula (III)
xe2x80x83ClCOO(CH2)nxe2x80x94Arxe2x80x83xe2x80x83(III)
wherein n is 1-7 and Ar individually stands for unsubstituted or substituted aryl groups with up to 18 carbon atoms, preferably with benzyloxycarbonyl chloride, in the presence of bases, preferably sodium hydrogen carbonate, in a reaction-inert solvent, preferably in benzene or toluene, yielding 2xe2x80x2-O,3xe2x80x2-N-bis(bezyloxycarbonyl)-3xe2x80x2(Kobrehel G. et al., U.S. Pat. No. 5,250,518; May 1993) of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2, R3, R7 and R8 are mutually the same and stand for hydrogen, R4 and R5 are mutually the same and stand for benzyloxycarbonyl group and R6 is hydroxyl group, which is subsequently subjected to silylation of hydroxyl groups in
A/ 4xe2x80x3- and 11-positions with 2-5 equimolar excess of a silylating agent, in an organic inert solvent, at the temperature of 0-5xc2x0 C. during 5-8 hours, yielding novel 4xe2x80x3-11-O-bis(trimethylsilyl)-2xe2x80x2-O,3xe2x80x2-N-bis(benzyloxycarbonyl)-3xe2x80x2-N-demethyl-azithromycin of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2 and R7 are mutually the same and stand for trimethylsilyl group, R3 and R8 are mutually the same and stand for hydrogen, R4 and R5 are mutually the same and stand for benzyloxycarbonyl group and R6 is hydroxyl group, or in
B/ 4xe2x80x3-position with 1.1-2 equimolar excess of a silylating agent, in an organic inert solvent, at the temperature of 0-5xc2x0 C. during 1 hour, yielding novel 4xe2x80x3-O-trimethyl-silyl-2xe2x80x2-O,3xe2x80x2-N-bis(benzyloxycarbonyl)-3xe2x80x2-N-demethyl-azithromycin of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2 stands for trimethylsilyl group, R3, R7 and R8 are mutually the same and stand for hydrogen, R4 and R5 are mutually the same and stand for benzyloxycarbonyl group and R6 stands for hydroxyl group.
As silylating agents there are used 1,1,1,3,3,3-hexamethyldisilazane, trimethylsilyl chloride, bis(trimethylsilyl)acetamide and similar agents for introducing trimethylsilyl group, preferably a mixture of trimethylsilyl chloride and trimethylsilyl imidazole. As a suitable solvent pyridine, ethyl acetate, N,N-dimethylformamide, methylene chloride and the like, preferably pyridine are used.
Step 2
By a reaction of 4xe2x80x3,11-O-bis(trimethylsilyl)-2xe2x80x2-O,3xe2x80x2-N-bis(benzyloxycarbonyl)-3xe2x80x2-N-demethyl-azithromycin from the step 1A/or 4xe2x80x3-O-trimethylsilyl-2xe2x80x2-O,3xe2x80x2-N-bis(benzyl-oxycarbonyl)-3xe2x80x2-N-demethyl-azithromycin from the step 1B/, respectively, with 1.3-10 moles of a corresponding alkylating agent, preferably methylating agent, in the presence of 1.1-8.5 moles of a suitable base, at a temperature from xe2x88x9215xc2x0 C. to room temperature, preferably at 0-5xc2x0 C., in a suitable reaction-inert solvent, there comes to
A/ a selective alkylation, preferably methylation of C-12 hydroxyl group yielding a novel 4xe2x80x3-11-O-bis(trimethylsilyl)-2xe2x80x2-O,3xe2x80x2-N-bis(benzyloxycarbonyl)-3xe2x80x2-N-demethyl-12-O-methyl-azithromycin of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2 and R7 are mutually the same and stand for trimethylsilyl group, R3 stands for hydrogen, R4 and R5 are mutually the same and stand for benzyloxycarbonyl group, R6 is hydroxyl group and R8 is methyl, or
B/ an alkylation, preferably methylation of C-11 or C-12 hydroxyl group yielding a mixture of novel 4xe2x80x3-O-trimethylsilyl-2xe2x80x2-O,3xe2x80x2-N-bis(benzyloxycarbonyl)-3xe2x80x2-N-demethyl-11-O-methyl-azithromycin of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2 stands for trimethylsilyl group, R3 and R8 are mutually the same and stand for hydrogen, R4 and R5 are mutually the same and stand for benzyloxycarbonyl group, R6 stands for hydroxyl group and R7 is methyl, or 4xe2x80x3-O-trimethylsilyl-2xe2x80x2-O,3xe2x80x2-N-bis(benzyloxycarbonyl)-3xe2x80x2-N-demethyl-12-O-methyl-azithromycin of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2 stands for trimethylsilyl group, R3 and R7 are mutually the same and stand for hydrogen, R4 and R5 are mutually the same and stand for benzyloxycarbonyl group, R6 stands for hydroxyl group and R8 is methyl.
As suitable alkylating agents there are used (C1-C12)alkyl halides, preferably methyl iodide, dimethyl sulfate, methyl methane sulfonate or methyl p-toluene sulfonate, preferably methyl iodide. Suitable bases are alkali metal hydride (lithium hydride, sodium hydride or potassium hydride), alkali metal hydroxide (potassium hydroxide or sodium hydroxide) or alkali metal methyl amide (lithium amide, sodium amide or potassium amide), preferably sodium hydride. Suitable reaction-inert solvents are dimethyl sulfoxide, N,N-dimethyl formamide, N,N-dimethyl acetamide or hexamethyl phosphoric triamide, preferably N,N-dimethyl formamide, dimethyl sulfoxide or a mixture thereof with tetrahydrofuran.
Step 3
4xe2x80x3-11-O-Bis(trimethylsilyl)-2xe2x80x2-O,3xe2x80x2-N-bis(benzyloxycarbonyl)-3xe2x80x2-N-demethyl-12-O-methyl-azithromycin from the step 2A/ or the obtained mixture of 4xe2x80x3-O-trimethylsilyl-2xe2x80x2-O,3xe2x80x2-N-bis(benzyloxycarbonyl)-3xe2x80x2-N-demethyl-11-O-methyl-azithromycin and 4xe2x80x3-O-trimethylsilyl-2xe2x80x2-O,3xe2x80x2-N-bis(benzyloxycarbonyl)-3xe2x80x2-N-demethyl-12-O-methyl-azithromycin from the step 2B/ is subjected to a hydrogenolysis reaction according to the method by E. H. Flynn et al. (Journal of American Chemical Society, 77, 3104, 1950) in order to deprotect protecting groups on 2xe2x80x2- and 3xe2x80x2-positions and then to desilylation according to the conventional process in lower alcohols, preferably isopropanol in the presence of formic acid in
A/ 4xe2x80x3- and 11-positions in the step 2A/ yielding 3xe2x80x2-N-demethyl-12-O-methyl-azithromycin of the general formula (I) wherein R1 stands for L-cladinosyl group of the formula (II), R2, R3, R4, R5 and R7 are mutually the same and stand for hydrogen, R6 is hydroxyl group and R8 is methyl, or in
B/ 4xe2x80x3-position in the Step 2B/ yielding a mixture of 3xe2x80x2-N-demethyl-11-O-methyl-azithromycin of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2, R3, R4, R5 and R8 are mutually the same and stand for hydrogen, R6 is hydroxyl group and R7 is methyl, and 3xe2x80x2-N-demethyl-12-O-methyl-azithromycin of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2, R3, R4, R5 and R7 are mutually the same and stand for hydrogen, R6 is hydroxyl group and R8 is methyl.
Hydrogenolysis is carried out in a solution of lower alcohols, preferably in ethanol, in the presence of NaOAc/HOAc buffer (pH 5) with a catalyst such as palladium black or palladium on charcoal, at a hydrogen pressure from 1 to 20 bars, at room temperature.
Step 4
3xe2x80x2-N-Demethyl-12-O-methyl-azithromycin from the step 3A/ or the obtained mixture of 3xe2x80x2-N-demethyl-11-O-methyl-azithromycin and 3 xe2x80x2-N-demethyl- 12-O-methyl-azithromycin from the Step 3B/ is subjected to a reductive 3xe2x80x2-N-methylation with 1-3 equivalents of formaldehide (37%) in the presence of an equal or double quantity of formic acid (98-100%) and hydrogenation catalyst or of some other hydrogen source, in a reaction-inert solvent such as halogenated hydrocarbons, lower alcohols or lower ketones, preferably chloroform, at the reflux temperature of the reaction mixture, yieldingxe2x80x94in the case of the compound from the Step 3A/xe2x80x9412-O-methyl-azithromycin of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2, R3, R4 and R7 are mutually the same and stand for hydrogen, R5 and R8 are mutually the same and stand for methyl and R6 is hydroxyl group, orxe2x80x94in the case of products from the Step 3B/xe2x80x94a mixture of 11-methyl-azithromycin of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2, R3, R4 and R8 are mutually the same and stand for hydrogen, R5 and R7 are mutually the same and stand for methyl and R6 is hydroxyl group, and of 12-O-methyl-azithromycin of the general formula (I), wherein R1, R2, R3, R4, R5, R6, R7 and R8 have the meanings as given in the case of 3xe2x80x2-N-methylation of the compounds from the Step 3A/.
Step 5
Azithromycin of the general formula (I), wherein R1 stands for L-cladinosyl group of the formula (II), R2, R3, R4, R7 and R8 are mutually the same and stand for hydrogen, R5 is methyl and R6 is hydroxyl group, or its 11-O-methyl- and 12-O-methyl-derivatives from the Step 4 are optionally subjected to hydrolysis with strong acids, preferably with 0.25-1.5 N hydrochloric or dichloroacetic acid in a mixture of water and an alcohol, preferably methanol, ethanol or isopropanol, for 10-30 hours, at room temperature yielding 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-3-oxy-azithromycin of the general formula (I), wherein R1 and R6 are mutually the same and stand for hydroxyl group, R3, R4, R7 and R8 are mutually the same and stand for hydrogen and R5 is methyl, or 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-3-oxy-11-O-methyl-azithromycin of the general formula (I), wherein R1 and R6 are mutually the same and stand for hydroxyl group, R3, R4 and R8 are mutually the same and stand for hydrogen and R5 and R7 are mutually the same and stand for methyl, or 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-3-oxy-12-O-methyl-azithromycin of the general formula (I), wherein R1 and R6 are mutually the same and stand for hydroxyl group, R3, R4 and R7 are mutually the same and stand for hydrogen and R5 and R8 are mutually the same and stand for methyl.
Step 6
3-De(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-3-oxy-azithromycin and its 11-O-methyl- and 12-O-methyl derivatives from the Step 5 are subjected to a selective acylation of the hydroxyl group in 2xe2x80x2-position. Acylation is carried out with chlorides or anhydrides of carboxylic acids with up to 4 carbon atoms, preferably with acetic acid anhydride, in the presence of inorganic or organic bases, in a reaction-inert organic solvent, at a temperature from 0-30xc2x0 C., yielding 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-3-oxy-azithromycin 2xe2x80x2-O-acetate of the general formula (I), wherein R1 and R6 are mutually the same and stand for hydroxid group, R3, R7 and R8 are mutually the same and stand for hydrogen, R4 is acetyl and R5 is methyl, or 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-3-oxy-11-O-methyl-azithromycin 2xe2x80x2-O-acetate of the general formula (I), wherein R1 and R6 are mutually the same and stand for hydroxyl group, R3 and R8 are mutually the same and stand for hydrogen, R4 is acetyl and R5 and R7 are mutually the same and stand for methyl, or 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-3-oxy- 12-O-methyl-azithromycin 2xe2x80x2-O-acetate of the general formula (I), wherein R1 and R6 are mutually the same and stand for bydroxyl group, R3 and R7 are mutually the same and stand for hydrogen, R4 is acetyl and R5 and R8 are mutually the same and stand for methyl.
As suitable bases there are used sodium hydrogen carbonate, sodium carbonate, potassium carbonate, triethylamine, pyridine, tributylamine, preferably sodium hydrogen carbonate. As a suitable inert solvent there is used methylene chloride, dichloroethane, acetone, pyridine, ethyl acetate, tetrahydrofuran, preferably methylene chloride.
Step 7
3-De(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-3-oxy-azithromycin 2xe2x80x2-O-acetate and its 11-O-methyl- and 12-O-methyl derivatives from the Step 6 are subjected to oxidation of the hydroxyl group in C-3 position with Jones reagent or diimides according to a modified Moffat-Pfitzner process [DMSO and 1-(3-dimethylaminopropyl)-3-ethyl-carbodiimide in the presence of pyridine trifluoro-acetate] yielding 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-azithromycin 3,6-hemiketal 2xe2x80x2-O-acetate of the general formula (I), wherein R1 stands for hydroxyl group, R3 together with R6 stands for an ether group, R4 is acetyl, R5 is methyl, and R7 and R8 are mutually the same and stand for hydrogen, or 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)- 11-O-methyl-azithromycin 3,6-hemiketal 2xe2x80x2-O-acetate of the general formula (I), wherein R1stands for hydroxyl group, R3 together with R6 stands for an ether group, R4 is acetyl, R5 and R7 are mutually the same and stand for methyl, and R8 is hydrogen, or 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribo-hexopyranosyl-oxy)-12-O-methyl-azithromycin 3,6-hemiketal 2xe2x80x2-O-acetate of the general formula (I), wherein R1 stands for hydroxyl group, R3 together with R6 stands for an ether group, R4 is acetyl, R5 and R8 are mutually the same and stand for methyl and R7 is hydrogen.
Step 8:
3-De(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-azithromycin 3,6-hemiketal 2xe2x80x2-O-acetate and its 11-O-methyl- and 12-O-methyl-derivatives from the Step 7 are subjected to solvolysis in lower alcohols, preferably in methanol, at a temperature from room temperature to the reflux temperature of the solvent, yielding 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-azithromycin 3,6-hemiketal of the general formula (I), wherein R1 stands for hydroxyl group, R3 together with R6 stands for an ether group, R4, R7 and R8 are mutually the same and stand for hydrogen, and R5 is methyl, or 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-1 1-O-methyl-azithromycin 3,6-hemiketal of the general formula (I), wherein R1 stands for hydroxyl group. R3 together with R6 stands for an ether group, R4 and R8 are mutually the same and stand for hydrogen and R5 and R7 are mutually the same and stand for methyl, or 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-12-O-methyl-azithromycin 3,6-hemiketal of the general formula (I), wherein R1 stands for hydroxyl group, R3 together with R6 stands for an ether group, R4 and R7 are mutually the same and stand for hydrogen, and R5 and R8 are mutually the same and stand for methyl.
Step 9
3-De(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-azithromycin 3,6-hemiketal from the Step 8 is subsequently optionally subjected to a reaction with ethylene carbonate in the presence of inorganic or organic bases, preferably potassium carbonate, in a reaction-inert solvent, preferably ethyl acetate, yielding 3-de(2,6-dideoxy-3-C-methyl-3-O-methyl-xcex1-L-ribohexopyranosyl-oxy)-azithromycin 3,6-hemiketal 11,12 cyclic carbonate of the general formula (I), wherein R1 stands for hydroxyl group, R3 together with R6 stands for an ether group, R4 is hydrogen, R5 is methyl and R7 and R8 together with C-11 and C-12 carbon atoms stand for a cyclic carbonate.
Pharmaceutically acceptable addition salts, which are another object of the present invention, are obtained by a reaction of the novel compounds of the general formula (I) with an at least equimolar amount of a corresponding inorganic or organic acid such as hydrochloric, hydroiodic, sulfuric, phosphoric, acetic, propionic, trifluoroacetic, maleic, citric, stearic, succinic, ethylsuccinic, methanesulfonic, benzene-sulfonic, p-toluenesulfonic, laurylsulfonic and similar acids, in a reaction-inert solvent. The addition salts are isolated by filtration if they are insoluble in the reaction-inert solvent, by precipitation with a nonsolvent or by evaporation of the solvent, most frequently by lyophilization.
Antibacterial in vitro activity of the novel compounds of the general formula (I) and their pharmaceutically acceptable addition salts with inorganic or organic acids on a series of standard test-microorganisms was determined in a Mueller-Hinton medium (Difco-Laboratories, Detroit, Mich.) by a conventional method of double dilution in accordance with recommendations of NCCLS (The National Committee for Clinical Laboratory Standards). Each test microorganism was inoculated to the final inoculum size of 5xc3x97105 cfu/ml and the incubation was carried out in an anaerobic manner at 37xc2x0 C. during 18 hours. The MIC in the liquid medium was defined as the lowest concentration of an antibacterial agent inhibiting visible growth in microdilutional containers. Control organisms were obtained from ATCC (The American Type Culture Collection). All standards were identified by a standard procedure and were storaged at xe2x88x9270xc2x0 C. The results of 12-O-methyl-azithromycin on standard test microorganisms and clinical isolates in comparison with azithromycin are shown in Table 1 and Table 2.
By determining the concentration of 12-O-methyl-azithromycin in serum after a single oral dosis of 20 mg/kg on a group of 36 male rats in time intervals from 0.25 to 24 hours it was established that the novel antibiotic was very fast absorbed in the serum. An analysis of the peaks suggested the existence of enterohepatic circulation. During 0.5 and 1 hours a rapid drop of concentration took place, which was followed by a repeated increase. The maximum substance concentration was achieved after 2 hours (Cmax 248.8 ng/ml). A secondary maximum was achieved 4 hours after the application. The half-life was 5.2 hours and the total AUC was 1993.4 h ng/ml.